Multiple telegraphy.



No. 707,007. Pate nted- Aug. 12, I902.

' M. l. PUPIN.

MULTIPLE TELEGBAPHY. (Application filed Feb. 98, 1894.)

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Du INVENTOR ,2 ATTORNEY NORRIS n'n'sns coy. Pnomuru'm wnsmnuron a c UNITED STATES PATENT OFFICE.

MICHAEL I. PUPIN, OF NEl/V YORK, N. Y.

lVl U LTIPLE TELEG RAPHY.

SPECIFICATION forming part of Letters Patent No. 707,007, dated August 12, 1902.

Application filed February 23,1894. Serial No. 501,092. (No modeL) To all whom it may concern:

Be it known that I, MIOHAEL'I. PUPIN, of

the city, county, and State ofNeW York,have

invented a new and useful Improvement in Multiple Telegraphy, of which the following is a specification.

The object of myinvention is tosend a large number of messages simultaneously over a single conductor by means of periodic currents of different periodicities.

My invention is based on the following in such a way as to make the natural period of the conductor equal to the period of the impressed electromotive force. The cond uctor and the electromotive force are then in electrical resonance. The process of adjusting the natural period of the conductor so as to render it resonant is called electrical tuning. The laws which underlie electrical tuning and electrical resonance are analogous to those which underlie acoustical tuning and acoustical resonance. This physical fact has been investigated by me, and a reference is made here to my publications, The American Journal of Science for March, April, and May, 1898, and Transactions of the American Institute of Electrical Engineers for May 17, 1893.

Having described the fundamental physical fact on which my invention is based, Ishall now state the broad features of my invention.

A resonant conductor offers under all couditions a smaller impedance to the electromotive force with which it is in resonance thantoanyotherelectromotiveforce. Hence a resonant conductor can act as a current-selector that is to say, if such a conductor forms part of a directly or inductively connected system of conductors uponwhich a number of electromotive forces of various periodicities or pitch are impressed then its impedance will be smaller to that one among these electromotive forces with which it is in resonance than to any other.

If in a system of conductorsconsisting of parts which are either directly or inductively connected to each other there are in each part adjustable self-induction coils and electrostatic condensers, then these coils and condensers can be adjusted in such away that each separate conductor will have a different predetermined natural period, and therefore each part will resonate to a periodic electromotive force of its own pitch' and this independently of the presence of other electrometive forces. Such a system of interrelated tuned conductors of different periodicities or pitches acts, therefore, inv consequence of its resonating properties, as a set of current-selectors. This discovery originated with me, and I made it known and discussed. it in an article published in the Transactions of the American Institute of Electrical Engineers, Vol. X, May 17, 1893. This selective system of conductors, in which various selective parts are connected to each other either directly or by induction and in which each separate selective part is tuned to a different natural period from the periods of the other selective parts by means of self-induction coils and condensers, forms the broad feature of my invention. The applicability of such a selective system of interrelated conductors to multiple telegraphy is now evident.

I also claim the broad method herein dis closed of distributing electrical energy no matter for what purpose it may be used, which method consists in throwing upon a common conductor a number of alternate currents of diiferent frequencies and distributing the several energies of these currents each selectively to a separate electrical translating device, and I also claim the method herein disclosed of tuning'the various selective partsto different periodicities. These methods can be effected by many different forms of apparatus. Therefore I do not limit myself with respect to my method claims of any specific form of apparatus.

In another application filed by me on December 29, 1897, Serial No. 664,357, I have claimed the apparatus herein shown for carrying out the method, the said claims on the apparatus having been removed from this application in compliance with a requirement of division made by the Patent Office.

In the accompanying drawings, which form a part of this specification, Figure l is an electrical diagram showing an arrangement of devices for carrying said application to multiple telegraphy into effect. Fig. 2 shows a modificatio I Referring now to Fig. 1, 1 is the common conductor, shown in the form ofa main line' connected at two points with, say, three telephone transmitters 2, 3, and 4, which are connected in circuit with the battery 5. The

secondary coils of the transformers x y z of these transmitters are connected in parallel 'on one side to the common conductor at 9 the common conductor at the point 9 simul The function of the keys 1516 17 taneously. in the circuitsmy zand of the three telephone-receivers T T T will be explained presently.- Suffice it to state here that of the instruments inserted in the transmitting branch conductors thetransmitter with its induction-coil and an auxiliary coil, as X, Y, orZ, in each secondary circuit are the primary parts and the key and the telephone are the auxiliary parts in the operation. At the receiving end of. the line, starting from point 10, I arrange any number, say, three branch circuits, at b 0, consisting, essentially, of coils L M N for furnishing the auxiliary self-induction and condensers O P Q for furnishing the auxiliary capacity by the proportioning of which self-inductionand capacity the receiving-conductors aretuned. All of these receiving-conductors are connected to the ground G The auxiliary parts of these three branch conductorsare the telephonereceivers R, R, and R, which are placed in inductive relation with coils L M N and the small coils surrounding permanent magnets or soft-iron cores Mn 71 and also three keys 19 20 21. j

I proceed to explain the operation of the instruments in any branch at the receiving end by the instruments in the corresponding branch at the transmitting end. Say it is required to send a message from transmitter 4 to branch at. It is to be understood that what follows is also true of any other branch, as Z) or c. The coil L has a predetermined selfinduction and the condenser O has a predetermined capacity, and their values have been predetermined in such a way as to render branch a resonant to a frequency C. Hence the operator at 4: will u-sea fork of frequency G. The telephone T is acted upon inductively by coil Z orany other convenient part of the circuit at the transmitting end. The sound of the telephone R calls the attengiven in the following way: Whenever the operator at 4 closes key 17, an alternating currentof frequency 0 passes to the branch at and by its action upon the magnet Z sets the diaphragm of the receiving-transmitter r in vibration, thus producing ast-rong induced curren't of the same frequency in the secondary coil of the transformer23 of this transmitter, which currentpassing through the coil of the sounder 24 repeats the signals sent by the key 17. This communication of signals will in no way be interfered with by the simultaneous transmission of signals between the circuits band c and the transmitters2 and '3 as long as these transmissions employ a frequency dilferent from the frequency employedin the branch a. It should also be observed that each receiving instrument, as 24, may have an adjustable condenser in series with it in order to reduce its electromagnetic impedance to a minimum for the'frequency to be used in the branch. It is also clear that we may have any number of branchesboth at the receiving and at the transmitting end also that each branch can operate simultaneously as receiver and transmitter, provided that it has both the receiving and the transmitting apparatus. In Fig. 1 the receiving apparat-usonly in the branches at b 0' is described. Thus in branch I) at'the receiving end is a key 20, coil M, condenser P, and ironcore or permanent magnet m. The core m operates the transmitter-diaphragm at r and local circuit25 and through thetransformer 26 the sounder 27. Similarly in branch 0 is a key 21, coil N, condenser Q, and iron core n. The core n operates the transmitter-diaphragm at r and local circuit 28 and through the transformer 29 the sounder 30; but Iwish it tobe clearly understood that in each branch, like a, we may have any number of receiving and transmitting apparatus all connected in multiplewith this branch and working with the same frequency. v 1

Referring now to Fig. 2, here the common conductor 1 instead of being connected directly with the local circuits at b c is inductively connected with them by means of transformers, the primaries 31 32 33 are inseries in the common conductor,- while the secondaries 34 35 36 are'included in the localcircuits. It will be noted, therefore, that in Fig. 1 the branch circuits at b c are in parallel with the common conductor, while in Fig. 2 theprimaries inducing the branch-circuits a Z) c are in series with the common conductor. They may also be in multiple.

I use the word interrelated in the sense that the receiving-circuits and the transmitting-circuits are all connected conductively or inductively with a common mainconductor.

I desire to direct especial attentionto the fact that I use no synchronicallymoving mechanism of any sort at opposite ends of the line, and need no apparatus which interferes with the selection effected. All that is required is that the various receiving branch conductors of the system shall be tuned in electrical resonance with the several periodic currents of previously-selected periodicity by properly proportioning the electromagnetic constants of said branch conductor and that the tuning may be done once for all.

It is of course to be understood that in the local circuits at b 0 will be disposed the means here shown to effect the tuning of each by varying the self-induction or the capacity, or both, and also that in place of telephonetransmitters I may use oscillators or vibrators or any other contrivances adapted to produce and transmit to line currents of diiferent predetermined periodicities; also that both at the transmitting and receiving ends the telegraph keys and sounders, here introduced merely for the sake of their simplicity, may be replaced by any suitable telegraphic transmitting and receiving apparatus.

Without limiting myself to the details shown, what I claim, and desire to secure by Letters Patent of the United States, is-

1. The method of distributing electrical energy which consists inthrowing upon a common conductor a number of alternate currents of different frequencies and distribu ting the several energies of these currents each selectively to a separate electrical device, substantially as described.

2. The method of distributing electrical energy which consists in throwing upon a common conductor simultaneously a number of alternate currents of different frequencies and distributing the several energies of these currents each selectively to a separate electrical device, substantially as described.

3. The method of rendering selective by electrical resonance various partsof a set of interrelated conductors wherein each part to be made selective contains a condenserand a self-induction coil, which consists in properly'proportioning the electromagnetic constants of the various parts to be made selective so that each such part becomes resonant to an electromotive force of predetermined periodicity, substantially as described.

4. The method of multiple telegraphy by rendering selective by electrical resonance the various parts of a multiple telegraphic system made up of a set of interrelated conductors and corresponding transmitting and receiving instruments in which each receiving instrumentis controlled by one of the parts to be made selective and each such part contains a condenser and a self-induction coil, the

method consisting in properly proportioning the electromagnetic constants of each selective part, so that it becomes resonant to an electromotive force of predetermined periodicity to be impressed on the line by the corresponding transmitting instrument, substantially as described.

MICHAEL l. PUPIN. Witnesses:

H. R. MoLLER, M. BoscH. 

